Differential pressure formed luggage with molded integrated frame

ABSTRACT

The invention relates to hard sided luggage shells and other containers manufactured using vacuum forming or pressure forming of thermoplastics. A process for making shells and containers with integrally molded frames is disclosed, and products made by the method. A method of manufacturing differential pressure formed containers with framed openings, but without the need to attach a separate frame element to the molded shell. A process also is disclosed for reducing the undesirable stretching of shell material that occurs during differential pressure forming, particularly the thinning of corner portions of the shell or container. The process of the invention more efficiently utilizes the thermoplastic material by moving material from otherwise offal portions into the molded product. An improved method for severing the offal material from the final product is disclosed.

This application is a continuation of Ser. No. 08/481,962 filed on Jun.7, 1995 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to vacuum formed and pressure formedproducts and processes, particularly hard sided luggage.

2. Background Art

Hard sided luggage usually consists of two shells, commonly called a lidshell and a base shell. Each shell typically is made from a sheet ofthermoplastic material that has been molded in the shape of a container.The shell frequently is shaped as a rectangular box with rounded cornerswhose open side is defined by a peripheral edge. The peripheral edges ofthe two shells substantially correspond to one another, so that the lidshell may be placed, concave side down, upon the base shell with itsconcave side up, so that the respective edges are aligned and/or incontact. So arranged, the shells may then be connected by hinges andreleasable latches, as known in the art, to define a container with anaccessible interior space.

A principal objective in hard sided luggage making is to provide a casethat is at once both lightweight and strong. Besides beingpuncture-proof and unbreakable, a hard sided case of ideal strength alsoresists gross deformation of its overall shape due to external torsionalor flexural forces. While some minor flexibility is desirable in a hardsided case, an advantage of hard sided luggage should be itsrigidity--the ability to withstand forces without undue amounts oftwisting or bending. Twisting of any type of luggage can jeopardize theluggage contents, and may also damage hinges and promote latch failure.

Shells incorporated in hard sided luggage are normally molded using oneof two manufacturing processes. Injection molding involves theinjection, under pressure, of molten thermoplastic resin, typicallypolypropylene, into massive steel molds to form substantially completeshells including integral frame and attachment points for wheels,handles, etc. The nature of injection molding processes and machinerylimit somewhat the ultimate configuration of the molded item. Injectionmolding also requires the use of very high pressure systems, which canbe expensive to acquire and maintain, and which may limit productvariety and rapid product modification.

The other main process, commonly called "vacuum forming," involvesforcing a heated sheet of thermoplastic against a male or female mold.The driving force is provided by a pressure differential, so that adifference in air pressure on opposite sides of the sheet causes thesheet to move against the mold. Strictly speaking, "vacuum forming"refers to the creation of a "negative," or reduced pressure in thevolume between the sheet and the mold, thereby pulling or "sucking" thesheet up to the mold. Alternatively, "pressure molding" involves thecreation of a volume of "positive," or elevated pressure on the side ofthe sheet opposite from the mold, thereby blowing or pushing the sheetto the mold. Moreover, pressure molding and vacuum molding can andfrequently are simultaneously performed within a single apparatus, andsuch combined processes sometimes are generically referred to as "vacuummolding." Unless the specific terms "vacuum forming" or "pressureforming" are used, this disclosure shall use the generic term "pressuredifferential forming," meaning vacuum forming alone, pressure formingalone, or a combination of the two processes.

In differential pressure forming, after the pliable heated sheet hasconformed to the shape of the mold surface, it is removed from the mold.The three dimensional shaped shells are then trimmed to proper size andto eliminate edge sections (sometimes called offal or selvage portions)needed for the process but not forming a part of the final product.Conventionally, in order for the resulting formed case to have adequaterigidity, the formed shell is riveted or stapled to a separate framecomponent--commonly a metal frame extruded from aluminum or magnesiumalloys. Hinges are attached to the frames, and other hardware and liningelements are then attached to form the completed case.

A disadvantage of the standard differential pressure forming processesfor making luggage is the need for the separate frame component to beattached to the shell. A typical differential pressure formed shell,alone, is relatively crush proof and puncture proof, has flexiblestrength yielding to stress, and is subject to both plastic and elasticdeformation when subjected to any considerable loading. The frame, onthe other hand, is light and strong, but comparatively inflexible. Thestiffness of the frame and the flexibility of the shell do notcompliment each other, especially at the local stress points where theshell and the frame are riveted or stapled together. At these points ofelevated stress, rivets or staples are prone to pull through or tear thethermoplastic shell. Also, the magnesium and aluminum frames add expenseto the manufacture of the case; the frame itself usually requires anumber of finishing steps because it is a principal aesthetic feature ofthe completed article of luggage. Also, the frame is typically used tohide the raw edge of the trimmed formed shell.

Another problem frequently encountered in conventional vacuum-formingcontainer manufacturing processes is undesirable thinning in the wallsof the finished product, particularly near corners and edges. This posesserious disadvantages to container strength, since corners and edgestend to be the portions of the container subject to elevated impact andbending stresses.

Still another problem encountered in the present art is the limitationsthat are imposed upon the shape of the final product by the need toremove the finished product from the mold. The finished product issimply pulled straightaway from the mold once the thermoplastic hascooled. In order for this separation to be accomplished without cuttingthe molded product, the mold must be shaped to provide that no part ofthe molded product interlocks with the mold itself; if a standard vacuummold surface has substantial projections or depressions into whichproduct material is forced, a the product will interlock with the moldto prevent the product from being pulled away from the mold in thedirection of attempted separation. Unfortunately in the present art,this limitation on the shape of the mold has hindered container design,including the design of integrally framed luggage shells.

Luggage shells have also been manufactured using blow molding androtational molding processes. Blow molding and rotational molding have avariety of limitations in luggage applications. For example, blowmolding and rotational molding processes have poor thickness control,resulting in thin spots in walls. These prior art processes are alsolimited as to the shapes and compositions of the products produced, anddo not permit ready lining or finishing of interior surfaces.

Thus a need remains for a luggage product manufactured using thecomparatively simple and inexpensive pressure differential moldingprocess, but which overcomes the disadvantages of present products andimproves upon the manufacturing process. Against this background, thepresent invention was developed.

SUMMARY OF THE INVENTION

The invention relates generally to differential pressure formed productsand processes, particularly hard sided luggage. The invention is acontainer, such as a luggage case shell, and making the container usingpressure differential pressure forming processes, which dispenses withthe need to attach a separate frame element to the formed product. Themaking of the product includes a process for molding a shell from asheet of plastic material, where the shell has a bottom and sidesextending from the bottom to a peripheral edge, and the intersections ofthe sides with each other and with the bottom define the shell corners.The process includes providing a sheet of thermoplastic material with acentral portion, a marginal portion, and a selvage portion; providing amold with a mold surface; positioning a portion of the sheet in the moldmeans in a confronting relation to the mold surface; conforming thecentral portion of the sheet to the mold surface; and shaping themarginal portion of the sheet to fashion a frame integrally formed withthe central portion of the sheet, with the frame extending substantiallycontinuously along at least a portion of the peripheral edge. Theinventive process may also include the steps of heating the sheet ofplastic material; partially surrounding a form space with a moldsurface; placing at least one movable side draw form in an extendedposition in the form space; forcing the central portion of the heatedsheet against the mold surface; forcing the marginal portion of heatedsheet against the side draw form while the side draw form is in theextended position to shape the marginal portion of the sheet to increasethe cross sectional moment of inertia of the shell at the peripheraledge; and then retracting the side draw form to a retracted position atleast partially exterior to the form space while the heated sheet isagainst the mold. A product of improved quality is produced bystretching certain parts of the sheet prior to supplying the pressuredifferential and by retarding the stretching, through cooling processes,of other sections of the sheet which form the shell corners. Also, theprocess for making the inventive product includes a mode of increasingthe volume of thermoplastic material in the portion of the sheet forcedagainst the mold through shifting material from the selvage portion ofthe sheet toward a location nearer the mold, by providing a clamp remotefrom the mold; holding the selvage portion of the sheet in the clamp;and permitting the selvage portion of the sheet to stretch away from theclamp and toward a location in confronting relation to the mold surface.

A primary object of the invention is to provide a mode of differentialpressure forming a container with an integrally formed frame.

Another object of the invention is to provide a differential pressureformed container product without a separately attached frame element.

A primary advantage of the invention is that a container product isproduced by methods providing improved container strength without a netincrease in materials requirements.

Other objects, advantages and novel features, and further scope ofapplication of the present invention will be set forth in part in thedetailed description to follow, taken in conjunction with theaccompanying drawings, and in part will become apparent to those skilledin the art upon examination of the following, or may be learned bypractice of the invention. The objects and advantages of the inventionmay be realized and attained by means of the instrumentalities andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, illustrate several embodiments of the presentinvention, and together with the written description serve to explainthe principles of the invention. The drawings are only for the purposeof illustrating a preferred embodiment of the invention and are not tobe construed as limiting the invention. In the drawings:

FIG. 1 is a perspective view of the preferred embodiment of the luggagecase apparatus of the invention, with the case partially open;

FIG. 2 is a front view of the FIG. 1 embodiment;

FIG. 3 is a front view of the luggage case apparatus of the invention,showing the case in a closed position;

FIG. 4 is a partial sectional side view of the luggage case apparatus ofthe invention in a partially open position, the section takensubstantially along section line 4--4 in FIG. 2;

FIG. 5 is a partial sectional side view of the FIG. 3 embodiment, thesection taken substantially along section line 5--5 in FIG. 3;

FIG. 6 is a partial enlarged sectional side view of the luggage caseapparatus of the invention, showing details of the latch and handleelements;

FIG. 7 is a top view of the preferred embodiment of the luggage caseapparatus of the invention, showing the case completely open;

FIG. 8 is a partial enlarged view of the hinge portion of the FIG. 7embodiment;

FIG. 9 is a partial enlarged view of the latch portion of the FIG. 7embodiment;

FIG. 10 is a partial enlarged view of the luggage case apparatus of theinvention in a slightly opened position, with portions broken away toshow details of the latch, handle, and catch elements;

FIG. 11 is a sectional side view of the preferred embodiment of themanufacturing apparatus of the invention, showing the platen assembliesin a separated relation;

FIG. 12 is a top sectional view of a portion of the FIG. 11 embodiment,the section taken substantially along section line 12--12 in FIG. 11,showing the side draw forms in a substantially retracted position;

FIG. 13 is sectional side view of the embodiment of FIG. 11, showing theplacement of a sheet of thermoplastic material to be molded;

FIG. 14 is a side sectional view of the preferred embodiment, showingthe side draw forms in a substantially extended position;

FIG. 14A is a partial enlarged sectional side view of a portion of theembodiment of FIG. 14, showing details of the pinch plate, side drawform, and seal plate elements, with the pinch off plate in a loweredposition;

FIG. 14B is another view of the FIG. 14A embodiment, showing the pinchoff plate in a raised position; and

FIG. 15 is a top view of the embodiment of FIG. 12, showing the sidedraw forms in a substantially extended position.

DESCRIPTION OF THE PREFERRED EMBODIMENT (BEST MODE FOR PRACTICING THEINVENTION)

The improvements of the present invention pertain to the manufacture ofhard sided luggage, although it will be understood that the principlesof the invention certainly may be used in the manufacture of containersgenerally. The advantages of the invention may be realized whenever itis desired to provide an integrally formed frame about a thinthermoplastic hollow shell with an opening into the shell bound by theintegrally formed frame.

Attention is invited to FIG. 1, which shows a perspective view of aluggage case 30 manufactured according to the invention. The item shownis a pullman style case, although the invention applies as well topopular "upright" luggage styles. Moreover, while the case 30 depictedin FIG. 1 has no wheels or wheel handle, it will be readily understoodthat alternative embodiments of the luggage apparatus of the inventionmay incorporate wheels and pull handles known in the art for allowingluggage to be wheeled, rather than carried.

Reference is made to FIGS. 1-3. The inventive case 30 includes a lidshell 40 and a base shell 80. The inventive process may be employed tomanufacture both the base shell 80 and the lid shell 40, and in thepreferred embodiment the shells 40,80 are very similar in theirconfiguration and shape. Optional variations of the invention mayinclude embodiments where only one of the shells of the case 30 ismanufactured according to the invention; indeed, one of the shells,perhaps the lid shell 40, may be made of stitched cloth panels,generally termed "soft side" construction.

In the preferred embodiment, each shell 40,80 is molded from a singlesheet of thermoplastic material. The invention is particularlywell-suited to the molding of sheets of acrylonitrile-butadiene-styrene(ABS). The invention also can be practiced using a vacuum-formable (e.g.a low melt index) polypropylene. Thus, the invention is applicable toforming polypropylene, and can make an inventive product that has theappearance of having been injection molded, even though it wasdifferential pressure formed.

The stock sheet typically is a rectangular and planar sheet of material,perhaps extruded, with marginal portions surrounding a central portion.In the description to follow, the sheet will be described with respectto a central portion, a marginal portion, and a selvage portion. Theselvage portion is a comparatively small proportion of the overallsheet, and is comprised of the border of the sheet adjacent to itsoriginal edges. The selvage portion is needed to secure the sheet withinthe vacuum-forming machinery; it does not become part of the finishedproduct but is trimmed away during or immediately after the moldingprocess. The central portion of the sheet is the bulk or majorityportion of the sheet that is molded to form the main part of the shell.The marginal portion, whose size in proportion to the central portionmay vary substantially from product to product, is the portion of thesheet defining the perimeter of the central portion; its outer limit isthe intersection with the selvage portion. The marginal portion becomesan integral part of the finished product, and effectively comprises theedge of the finished shell once the selvage is trimmed away. The sheetis heated to render it flaccid and pliable, and while in a flaccid stateit is molded to assume a shape similar to base shell 80 illustrated inFIG. 1.

Except for where otherwise noted, description of the base shell 80serves to describe the lid shell 40 as well. In the preferredembodiment, each formed shell 40,80 obtains a generally concave shapewith a bottom portion 81 and integral side portions 83a,83b which extendaway from bottom portion 81. The side portions 83a,83b and bottomportion 81 thus enclose on five sides the interior space of the shell 80in which items may be stored. The apparatus of the invention is notlimited to any particular overall shape, however, and may includecylindrical containers The molding and shape of certain facets of theside portions 83a,83b are an aspect of the invention, and will befurther explained.

Side portions 83a,83b extend away from bottom portion 81 to a rim 86.The lid shell 40 has a lid shell rim 46, and base shell 80 has a baseshell rim 86. Rims 46,86 preferably extend about the entire perimeterdefined by the side portions of the respective shells 40, 80.Preferably, but not necessarily, when the case 30 is completely closedand placed upon a horizontal supporting surface, the rim 86 occurs wherea plane tangent to the plenum of the shell 80 is substantiallyperpendicular to the supporting surface, as illustrated in FIG. 3.

Both shells 40,80 are shaped to provide an integrally molded frame abouttheir respective rims 46,86. This frame presents tremendous advantages,in that it is integrally molded with the shell, e.g., being formed fromthe same sheet of thermoplastic as the shell. The formation of anintegral frame eliminates the need to staple or otherwise attach aseparate frame, e.g. an extruded magnesium hoop, to the shell. Thisreduces tremendously the time and cost of manufacture, and obviates theproblems associated with coupling a separate rigid frame to a flexibleshell.

Combined reference is made to FIGS. 1 and 2. General description of theshell 80 continues to describe corresponding and analogous components ofthe lid shell 40 as well. In the preferred embodiment, the integrallymolded frame includes a wall member 82 depending from the shell 80 inthe vicinity of the rim 86, and a flange 84 extending from the wallmember 82. Each of shells 40,80 has a wall member 42,82 extendinginwardly, (that is, into and toward the interior space) from therespective rims 46,86. Lid shell 40 has lid shell wall member 42 andbase shell 80 has base shell wall member 82. As shown in FIGS. 1, 2 and7, each wall member 42,82, like the rims 46,86, preferably (but notnecessarily) runs about the full perimeter of the case 30. In thepreferred embodiment, wall members 42,82 depend perpendicularly from therims 46,86 of the respective shells 40,80, i.e., wall member 82 issubstantially parallel to a horizontal supporting surface upon which thecase 30 might be placed (FIG. 3). Thus, the angle as seen in crosssection (in FIG. 4, for example) that the wall member 82 makes relativeto the immediate adjacent side portions 83a or 83b of shell 80preferably is about ninety degrees. In alternative embodiments, however,the angle between a shell side portion and its depending wall member maybe oblique at any suitable angle.

Projecting from the respective wall members 42,82 are base flange 84 andlid flange 44. Like the wall members 42,82, flanges 44,84 are integrallymolded from the same sheet of thermoplastic as their correspondingshells 40,80. Shell 80, wall member 82, and flange 84 thus are notseparable components, but rather are extensions of one another allmolded from the single original thermoplastic sheet. One of the flanges44,84, preferably the lid flange 44, extends perpendicularly from itsrespective wall member 42. As illustrated in FIGS. 1 and 2, flanges44,84 extend outward from wall members 42,82, that is, they project awayfrom the interior space.

The free edges of the flanges 44,84 define the respective peripheraledges 48,88 of shells 40,80. Peripheral edges 48,88 run about theperimeter of the open side of each shell 40,80, and thus circumscribethe opening and establish its dimensions.

As shown in FIGS. 1-3 and 7, base shell 80 and lid shell 40 areconfigured to be used in conjunction, the lid shell 40 aligned atop thebase shell 80. When the case 30 is closed (FIG. 3) the peripheral edges48,88 register in close proximity. The shells 40,80 are pivotallyconnected together along corresponding lengths of their respective backsides 45,85 (FIG. 1). The pivotable connection preferably is by a pairor more of hinges 71,71', or a single length of piano hinge, or thelike. Accordingly , the lid shell 40 may by swung upward from base shell80 to expose the interior storage space of the case, or may be loweredto completely enclose and define the interior space.

Alternative embodiments of the case 30 may be hingeless. For example, acase or box container may be composed of a lid that slides straight downonto the base, in a manner common to hat boxes and shoeboxes. In such anembodiment, the flanges 44 and 84 still slide past one another in anoverlapping fashion; the lid shell 40 and the base shell 80 simply arecompletely separable with no hinged connection. Claw bolt or other typesof latches on one of the shells engage a ridge or ridges around theother shell to secure the shells together.

FIGS. 4 and 5 show enlarged cross sections of portions of the inventiveluggage case 30. These figures depict in further detail the specificconfiguration of the integral frame feature of the apparatus of theinvention. FIG. 4 is a sectional view of the shells 40,80 takensubstantially along line 4--4 in FIG. 2, as the shells 40,80 areoriented when case 30 is partially ajar. FIG. 5 shows, in cross sectiontaken substantially along line 5--5 in FIG. 3, the relative position ofthe elements of the integral shell frames when the case 30 is closed.Shells 40,80 may be molded in a gentle curved cross section extending totheir respective rims 46,86. At each rim 46,86, the shells 40,80 arebent inward, according to the process hereinafter described, to createwall members 42,82. In the preferred embodiment, each of wall members42,82 projects into the interior space contained by the case 30,substantially perpendicular to the imaginary plane that is tangent tothe curve of the respective shell 40,80 at its rim 46 or 86. The inwarddistance that wall members 42,82 project is not absolutely critical, butit must be substantial (e.g. about 3.0 cm on a standard sized pullmancase) in order to provide the desired cross sectional moment at theperimeter of the shells, and thus the appropriate rigidity to the shells40,80.

Depending from the lid shell wall member 42 and from the base shell wallmember 82 are lid flange 44 and base flange 84, respectively. The shellflanges 44,84 are fashioned substantially concurrently with theformation of the wall members 42,82, using the same inventive process.Like the wall members 42,82, the shell flanges 44,84 are molded from thematerial of the original sheet of thermoplastic, and thus are integralextensions of their corresponding wall members 42,82. In the preferredembodiment lid flange 44 projects perpendicularly from wall member 42;the lid flange 44 member extends downward toward the base shell 80. Baseflange 84 extends upward toward the lid shell 40, as shown in FIG. 4.The base flange 84, however, preferably is canted or obliquely tiltedwith respect to base wall member 82. It has been determined thatproviding base flange 84 with a slight inward (toward the enclosedspace) tilt encourages the lid flange 44 to smoothly and automaticallyslide past and around the base flange 84, promoting an automaticalignment and registration of the shells 40,80 during closure of thecase 30.

The dimensions and general cross-sectional configuration of the baseflange 84, base shell wall member 82, the lid flange 44 and the lidshell wall member 42, preferably are uniform throughout their occurrencearound the perimeters of the shells 40,80. It is noted, however, thateffective alternative embodiments of the invention may vary thedimensions (or configuration) of the wall members 42,82 and flanges44,84, as a function of their specific location upon the perimeter ofthe respective shell 40 or 80. Moreover, alternative embodiments of theinvention may involve interruptions in the flanges 44,84 and/or the wallmembers 42,82 to accommodate other structural elements, reduce weight,or to address other concerns. Thus, while in the preferred embodimentthe frame consisting of the wall members 42,82 and shell flanges 44,84extends completely around the opening of each shell 40,80, alternativeembodiments may provide the frame element only to certain portions ofthe shell perimeter.

Molding a thermoplastic sheet to fashion and incorporate the wallmembers 42,82 and flanges 44,84 into the shells 40,80 thus presents theadvantage of creating an integrated frame, dispensing with the need toattach a separate frame component to the shell. Each shell 40,80 isstiffened and stabilized by the rigidity provided by its associatedflange 44 or 84 and especially by its respective wall member 42 or 82.This increased rigidity is observed in any single shell 80 considered inisolation (e.g. when the case 30 is open, or in those embodiments of theinvention which incorporate only one hard shell). The additionalstiffness results from the moment of inertia of the cross section of theshell 80, flange 84, and wall member 82 in the immediate vicinity of rim86. The moment of inertia of the flange 84, wall member 82 and shell 80,with respect to any imaginary axis within the shell 80 (and, say,parallel to the rim 86), is increased due to the relative displacementof the shell flange 84 from the shell 80. By offsetting the flanges44,84 from their respective shells 40,80, and rigidly connecting theshells and flanges with wall members 42,82, the shells' resistance tobending is dramatically improved. The wall member 82 and flange 84combination effectively serves as an L-beam frame around the opening ofthe shell 80, fully integrated with the shell 80.

A noteworthy aspect of the preferred embodiment of the apparatus of theinvention is the operational relationship of the lid shell wall member42 and lid flange 44 with the base shell wall member 82 and the baseflange 84. The relationship is best understood with reference to FIGS.2, 4 and 5. FIG. 5 shows, in cross section, the relative positions ofthe two shells 40,80 and their respective integral frames when the case30 has been completely closed, as in FIG. 3. These figures illustratethat in the preferred embodiment the lid shell wall member 42, the lidflange 44, the base shell wall member 82, and the base flange 84, aredeliberately dimensioned so as to cooperate to provide an improved case.The cooperation of the lid shell frame with the corresponding elementsof the base shell 80, provides an improved mode of case closure, as wellas to increase the rigidity and security of the closed case.

FIG. 5 shows that when the case 30 is closed, an overlappingrelationship is provided between the lid flange 44 and the base flange84. Lid shell wall 42 extends inward from the lid shell 40 a distancesomewhat less than the distance the base shell wall member 82 extendsinward. The difference in distances preferably is approximately equal tothe combined thicknesses of the two flanges 44,84. Accordingly, theperimeter dimension of the base shell peripheral edge 88 is slightlyshorter than that of the lid shell peripheral edge 48. FIGS. 4 and 5also show that base flange 84 extends in length a distance slightlylonger than the distance extended by lid flange 44 (e.g. the differencein distances is approximately equal to the thickness of one of theflanges). These differences in dimensions between the frame componentsof the lid shell 40 and the corresponding components of the base shell80 provide for the overlapping relationship depicted in FIG. 5 when theshells 40,80 are brought together to close the case. Lid flange 44overlaps, and mildly slidably contacts, the base flange 84. Also, whenthe case 30 is closed the lid shell peripheral edge 48 preferablycontacts the base shell wall member 82.

An added benefit of the configuration of flanges 44,84 is that theyinteract during the closure of the case 30 to cause case 30 to closeproperly. The shells 40,80 are essentially self-aligning during closure,because the peripheral edge 48 of the lid shell 40 is slightly greaterin circumference than the peripheral edge of the base shell 80, andbecause the shells 40,80 are hinged together at at least one point so asto place the lid flange 44 to the outside of the base flange 84 (FIG.8). The lid flange 44 will always slide to the outside and around thebase flange 84, and then register against the base shell wall member 82as shown in FIG. 5, even if the two shells 40,80 were not properlyaligned at the inception of closure.

This arrangement of the flanges 44,84 and wall members 42,82 when thecase 30 is completely closed offers advantages of strength. FIG. 5 showsthat when the case 30 is closed, the wall members 42,82 preferably aresubstantially parallel but spaced apart a distance (e.g., approximately3.0 cm in a typical pullman case). Accordingly, when the case 30 isclosed, the wall members 42,82 and flange 44,84 elements of therespective shells 40,80 function cooperatively to form a type of U-beamframe around the perimeter of the case 30; the wall members 42,82 serveas the legs of the U-beam while the flanges 44,84 function as the backof the beam. This cooperative strengthening function is dramaticallyenhanced when the shells 40,80 are latched together, for example, when alatching mechanism securely links one wall member 42 to the other wallmember 82. This cooperation of the flanges 44,84 and the wall members42,82 of both shells 40,80 to form a sort of U-beam frame around theclosed case 30 serves to dramatically increase the case's resistance tobending, warping, or buckling. Thus, while lacking an expensive,separately attached frame, the case 30 nevertheless offers substantiallysecure storage of contained articles. Externally applied forces arereadily transmitted from either shell to the other shell, via the wallmembers 42,82 and flanges 44,84.

Additionally, the overlapping and engaged flanges 44,84 and wall members42,82 serve to strengthen the case 30 against carrying loads when thecase 30 is filled, closed, and carried by the carry handle 34. In thepreferred embodiment, shown in FIGS. 3, 5, 6 and 10, the carry handle 34of the case 30 is securely attached to the wall member 42 of lid shell40. Accordingly, the forces from the weight of the loaded case 30 areinitially transmitted from the handle 34 to the lid shell 40. But, inthe preferred embodiment, these carrying loads, besides being disbursedthroughout and borne by the lid shell 40, also are directly transmittedfrom the carry handle 34 to the lid shell wall member 42, thence to thecatches 39,39', thence to the latches 90,90', and thence to the baseshell wall member 82 for transmission to the base shell 80 itself. Someloading forces (such the weight of a user sitting on the case while thecase is in an upright position, as well as carry forces originating atthe handle 34) also are transmitted from the lid flange 44 directly tothe base flange 84, and thence to the base shell wall member 82 to bedistributed through the base shell 80. The overlapping configuration ofthe flanges 44,84, the engagement of alignment pins 110,110' intoalignment apertures 111,111', and the use of a latch 90 and catch 39 toconnect in a bridge-like manner the opposing wall members 42,82, thuseffectively transfer throughout the case 30 the load forces imposed uponthe case 30 originating at the handle 34 or elsewhere.

FIG. 8 details the pivotable connection of the lid shell 40 to the baseshell 80 using one or more hinges 71. The mode of connection shown inFIG. 8 has hinge 71 being secured, with screws, rivets, or the like, tobase shell wall member 82 and to lid flange 44. For added strength anddurability, the hinge 71 may be adapted to be secured to the lid shellwall member 42. The hinge 71 thus is mounted to the stiffest, strongest,parts of the shells 40,80--the integral frame elements defined by theflanges 44,84 and the wall members 42,82. Hinge 71 is fixedly positionedupon the base shell wall member 82 so as to provide that the lid flange44 may swing into overlapping position relative to the base flange 84when the lid shell 40 is closed down onto base shell 80. When the case30 is completely closed, the hinge 71 is on the outside of the case 30,with the lid flange 44 disposed between the hinge 71 and the base flange84.

FIGS. 2, 6, 7, and 10 collectively show the preferred attachment of thecarry handle 34 to the lid shell 40, and the preferred attachment of atleast one latch 90 to the base shell 80. The attachment to the lid shell40 of the handle assembly consisting of the handle 34, handle bezel 35and handle base 36, while the latches 90,90' are attached to the baseshell 80, is a departure from convention in the art. In the known art,the handle assembly and the latches typically are all mounted on thebase shell, often for reasons related to the provision or configurationof the separate metal alloy frame. The apparatus of the inventionpermits handle 34 to be securely mounted to the lid shell 40, which isan advantage to the user. Intuitively, a handle 34 should be placed uponthe lid shell 40, where it can serve as a grip with which to lift thelid shell 40 when opening the case 30.

The latches 90,90' of the preferred embodiment, however, are on the baseshell 80. In the preferred embodiment, the latches 90,90' engage withcatches 39,39' on lid shell 40 to secure the case 30 in a closedposition.

Attention is invited to FIGS. 6 and 10, detailing the attachment of thehandle 34 to the lid shell 40. Handle 34 and handle bezels 35,35' arefixedly connected to handle base 36. Handle base 36 preferably issecurely mounted, as with rivets 38,38' or the like, upon the outsideface the lid shell wall member 42. Preferably, but optionally, a thin,rigid, backing plate 37 (FIG. 6) may be mounted upon the inside surfaceof the lid shell wall member 42, opposite the handle base 36, to providereinforcement and a non-compressible surface against which to turn nutsor pull a rivet. Mounting the handle base 36 to the lid shell wallmember 42 is preferred to mounting it upon the lid flange 44, since theflange 44, being remotely cantilevered from the body of the lid shell40, is somewhat more prone to flexural bending or breakage.

FIGS. 6, 7, and 10 show that projecting through the handle base 36 arecatches 39,39'. Each catch 39 is fixed to lid shell wall member 42 andextends inwardly to define a small space between catch 39 and the insidesurface of lid shell wall member 42. Catch 39 is engaged by elements oflatch 90 to lock the case 30 closed, in a mode hereafter described.

FIGS. 6, 7, and 10 also depict that case 30 preferably is equipped witha pair of latches 90,90' for securing the shells together to lock thecase 30 in a closed position. Alternative embodiments of the apparatusof the invention may feature one, three, or even four latchingmechanisms. In the preferred embodiment, latches 90,90' arespring-operated "lift-lever" type latches. The general features andoperation of lift-lever type latches are known in the art; however, thelatches 90,90' incorporated in the preferred embodiment of thisinvention are modified to operate in an innovative manner and areunconventionally attached to the case 30. As the drawings show, thelatches 90,90' are attached to the base shell 80. Importantly, thelatches 90,90' are mounted upon the base shell wall member 82, andpreferably are not mounted upon and do not contact the base flange 84.In the preferred embodiment, the latch 90 is spaced away from the baseflange 84, to provide a gap or slot space between the bottom of thelatch 90 and the base flange 84.

As best shown in FIGS. 6, 9 and 10, a latch 90 is securely mounteddirectly to the outside face of the base shell wall member 82 usingrivets 91,91' or the like. The screws or rivets 91,91' pass through thelatch 90, penetrate the base shell wall member 82, and may be securedwith nuts or the like. An optional latch backing plate 89 may be placedon the inside of base shell wall member 82 to provide reinforcement anda rigid surface against which to turn nuts or pull a rivet.

FIGS. 6 and 10 show how the mode of mounting the handle base 36 and thelatch 90 avoids interfering with the overlapping engagement of the twoflanges 44,84. Both latches 90,90' function the same and engage otherelements of the case 30 in the same way, so description of one latchserves to describe both. Because latch 90 is mounted upon the base shellwall member 82 removed somewhat remotely from the base flange 84, aspace is provided between the latch 90 and the base flange 84 into whichthe lid flange 44 may be slidably inserted. Thus, when the case 30 iscompletely closed, the lid flange 44 nestles against the base flange 84,with the lid shell peripheral edge 48 against the base shell wall member82 (as seen in FIG. 5), without any interference from the latch 90. Whenthe case 30 is closed, a portion of the lid flange 44 thus is smoothlyinterpositioned between the bottom of the latch 90 and a portion of thebase flange 84. The invention thus permits the shells 40,80 to belatched together without projections or apertures of any sort having topenetrate either the base flange 84 or the lid flange 44.

FIGS. 2, 3, and 10 show that the case 30 closes with the handle 34 andhandle base 36 disposed between the two latches 90,90'. The interiorends of the latches 90,90' substantially align with correspondingexterior ends of the handle bezels 35,35'. The handle bezels 35,35'feature a space between a portion of each bezel 35,35' and the lidflange 44, so that an abbreviated portion of each latch 90,90' fitsunder a portion of a corresponding bezel 35,35' when the case 30 isclosed, as suggested by the detail of FIG. 10. Thus, the case 30 canclose completely, with the lid flange 44 on the exterior of, andsurrounding, the base flange 84, and yet with the latches 90,90' alsofully accessible on the exterior of the case 30, as shown in FIG. 3.

Conventional lift lever latches known in the art typically are"bottom-mounted" in that they are attached to the luggage by means ofscrews or rivets passing through the latch's bottom plate and into theluggage frame. Likewise, most latch levers generally are"bottom-locking." Bottom-locking latch levers utilize a lock cylinderwhich passes through the bottom plate of the latch lever and through theframe of at least one shell, in order to lock the latch to the frame andthereby secure the shells together.

Latch 90 of the present invention, shown enlarged in FIGS. 9 and 10, issimilar, in general operation, to lift lever latches known in the art,but is distinguishable from known devices in that it is innovativelyside-mounted rather than bottom-mounted, and locks solely to its ownbottom plate 92, rather than to a frame member. As previously mentioned,a side of latch 90 is attached to the wall member 82 of the base shell80; the bottom plate 92 of the latch 90 is not used to fix the latch 90to the shell 80. (Attachment of the latch 90 to the shell 80 moreaccording to standard practice would involve screwing or bolting thebottom plate 92 directly to the base flange 84.)

Similarly, latch 90 is side-catching. Latch 90 has hooked bolt 94, whichextends from the side of the latch 90. Hook bolt 94 is engageable withthe catch 39 protruding from the handle base 36; engagement of bolt 94with catch 39 serves (with hinges 71,71') to securely latch lid shell 40to base shell 80 when case 30 is closed. Thus, latch 90 features alateral catching feature.

Continued reference is made to FIGS. 9 and 10, which illustrate aconfiguration of latch 90. Latch 90 has a main body 93 which is securelyattached to the wall member 82 of the base shell 80. Main body 93 hasrail 95 upon which shuttle 96 may glide, that is, shuttle 96 is slidablyattached to rail 95. Grip lever 98 is manually lifted and lowered todisengage and engage the latch 90. Grip lever 98 is pivotally connectedto shuttle 96 by means of an axle pin 97. Axle pin 97, which runsthrough both lever 98 and shuttle 96, preferably also is disposedthrough slots in rail 95, so that shuttle 96 may slide horizontally(i.e. parallel to base flange 84) to and fro upon rail 95, but isconstrained against up and down motion (perpendicular to base flange84). Hook bolt 94 is rigidly or integrally attached to, and extendslaterally from, shuttle 96. Grip lever 98 also is swingably connected tomain body 93 by link arm 99 which is pivotally connected at its ends tolever 98 and body 93 respectively. Pivotally disposed at the distal endof lever 98 are tab 101 and claw 102. When the case 30 is closed, griplever 98 may be depressed, causing claw 102 to interengage with cleat100. An elastic member 104, such as a spring or the like, connectsshuttle 96 to main body 93, and biases shuttle 96 toward the distal endof the main body 93, i.e., toward the cleat 100.

The figures show the components of the latch and handle assemblies asthey might appear immediately prior to the shutting of the case 30, andaid in the understanding of the operation of the latch 90. Latch 90 isin an open position, with lever grip 98 lifted. When the case 30 iscompletely closed, the peripheral edge 48 of the lid flange 44preferably abuts the outside face of the base shell wall member 82, anda portion of the latch 90 moves under the protruding portion of thehandle bezel 35. With the case 30 closed, grip lever 98 is depresseddownward; as the lever is pushed downward toward the lid flange 44, itpivots about both the axle pin 97 and the link arm 99 (while the linkarm 99 also swings around its connection with main body 93).Concurrently, the shuttle 96 glides upon the rail 95, against thetension force of the elastic member 104, as the entire grip lever 98shifts downward and slightly toward the proximal end of the body 93,i.e., toward the handle 34.

When the lever 98 has been completely depressed, it is substantiallyparallel with the bottom plate 92 of the main body 93 and with both theflanges 44,84 (which now overlap). Shuttle 96 is translated to itsmaximum position proximate to the handle bezel 35, which causes hookbolt 94 to engage catch 39. The insertion of hook bolt 94 between catch39 and lid shell wall member 42 latches the shells 40,80 together byconnecting their respective wall members 42,82. The latching is securedby the engagement of claw 102 with cleat 100. This engagement may bedoubly assured with the actuation of the key lock 103 cylinder upon griplever 98, if desired. Key lock 103, when engaged, secures the grip lever98 to the bottom plate 92, which prevents grip the lever 98 from beinglifted to disengage the hooked bolt 94 from the catch 39. The latch 90of the invention is distinguishable from prior lift lever latches inthat the grip lever 98 locks directly and only to bottom plate 92, andnot the base flange 84, which allows the opposing shell flange 44 to beinserted between the latch 90 and the flange 84. When the case 30 isclosed and the latch levers 98 depressed, the latches 90,90' aredesirably recessed at least in part within the channel defined by thewall members 42,82 and the lid flange 44.

The shells 40,80 are unlatched by repeating the latching process inreverse progress. Tab 101 is first lifted to release claw 102 from cleat100. A slight upward tug on the lever 98 pulls the lever 98 from itsclosed position, at which time the energy stored in the stretchedelastic member 104 is released, causing the shuttle 96 to be quicklypulled along the rail 95 toward the distal end of the latch 90, with theresult that the lever 98 rotates around axle pin 97 and link arm 99, and"pops" upward to a fully distended position, as shown in FIG. 9. Theshuttle 96 is pulled to its maximum distal position (away from handle34) by the elastic member 104, which results in a concomitant movementof the hook bolt 94, thus disengaging it from the catch 39. The user maythen grip the handle 34, and lift the lid shell 40 and swing it up andaway from the base shell 80 to open the case 30.

The lift lever 90, however, is substantially independent of anyparticular feature of either shell 40,80. It is lockable to itself(rather than to an opposing shell element) using the cleat 100 and claw102, and engages a catch 39 which is mountable virtually anywhere uponan opposite shell. Consequently, the latch functions with a minimum ofweakening penetrations through the shells.

FIGS. 2, 7, and 10 show an auxiliary system for guiding the properalignment of the two shells 40,80 upon closure of the case 30.Protruding rigidly from the side of handle base 36 are one or morealignment pins 110,110'. Corresponding pin apertures 111,111' occur inthe base shell wall member 82. Pins 110,110' align with the pinapertures 111,111', and, during closure of the case 30, pins 110,110'are inserted into apertures 111,111'. While the case 30 is closed, theengagement of pins 110,110' with apertures 111,111' helps preventparallel relative shifting of the overlapping flanges 44,84. Pins110,110' also assist in the transfer of shear forces between the twoshells 40,80 of the case 30; when a loaded case 30 is held in an uprightposition, the load forces are transferred between the wall members 44,84via the contact of the pins 110,110' with the base wall member 84.

It is seen therefore, that the mode and apparatus for latching theshells 40,80 of the invention together provides for secure closure ofthe case 30 without any need to penetrate the flanges 44,84 with anyholes, bolts, screws, catches, or other components. This advantageouslack of any apertures through, or attachments to, the flanges 44,84results in stronger flanges and the unobstructed overlapping of theflanges to permit a smooth, unimpeded closure of the case 30. Also,limiting attachments of both the latches 90,90' and the handle 34 to theoutwardly facing surfaces of the walls 42, 82 respectively help simplifyfactory assembly. The shells 40,80 are conveniently held on a horizontalwork surface (such as in FIG. 7), and various screw fasteners areinserted from above to attach, in a "top down" manner, the respectivehardware assembly to the wall members 42,82. Since nothing is affixed tothe flanges 44,84, there is no need for complex positioning devices tohold the shells 40,80 vertically, and to rotate and/or reposition theshells, to aid in inserting fasteners through the flanges.

As shown in FIGS. 4-6, the shells 40,80 may be molded with one or morebumper strip channels 50,50' which are shallow channels or mild groovesrunning around the perimeter of the shell 40,80 near the rim 46 or 86.Strip channels 50,50' are optional features used to enhance theappearance of the shell. Strip channels 50,50' may receive and retainbumper strips. Bumper strips (not shown) lengths of resilient ribbon orcord wrapped around the perimeter of a luggage shell to absorb some ofthe ordinary wear and tear to which the luggage is subjected. The bumperstrip often is colored in a hue that is complimentary or pleasantlycontrasting to the color of the shell 40 or 80, and thus serves the dualpurpose of improving the aesthetics of the case 30 as well as extendingits life. The process of the invention also promotes the ability to moldother desirable functional and/or aesthetic features into the shells inthe general vicinity of the shell rims 46,86.

Known pressure or vacuum forming devices and systems cannot manufacturethe luggage apparatus as described. In present systems, the formation ofthe wall members 44,84 and/or the flanges 44,82 in the configurationsshown (i.e. walls 42,82 projecting substantially perpendicularly inwardfrom side portions 83a,83b) would seriously impede the removal of themolded product from the mold. The wall members 42,82 would tend to catchupon, or "hang up" on the corresponding annular shoulder portion of themold which formed the wall members, locking the product in the mold.

FIGS. 11-15 depict the principal components of the inventive apparatusfor performing the process of the invention. The apparatus includes anupper platen assembly 200 and a lower platen assembly 240, positioned inparallel opposition to each other, preferably horizontally, one abovethe other. Hydraulic or other known systems permit upper platen assembly200 and lower platen assembly 240 to be moved perpendicularly withrespect to each other, e.g. closer or further apart. Known technologiespermit the controlled adjustment of the distance between the platenassemblies 200,240, by moving either the upper platen assembly 200 orthe lower platen assembly 240, or both of them. The platen assemblies200,240 accordingly may be substantially separated, or may be broughtinto contact. FIGS. 11 and 13, for example, show the platen assemblies200,240 in widely separated positions, while FIG. 14 shows the platenassemblies 200,240 drawn near together.

In the preferred embodiment, upper platen assembly 200 includes vacuumbox 202 and shell mold 206. As illustrated generally in the figures,shell mold 206 has an outside surface 207 and an inside surface 208; thelatter is the mold surface which serves to define the shape to which theproduct is molded. In the invention, the shell mold 206 is removable andinterchangeable, permitting the use of the apparatus to manufactureluggage shells, or other product, in a virtually unlimited assortment ofshapes, surface finishes, and surface features. The outside surface 207of shell mold 206 functions in conjunction with vacuum box 202 to defineand substantially surround the evacuation space 210. Shell mold 206 isin sealed contact with the vacuum box 202. Vacuum box 202 has one ormore vacuum orifices 205 connected to a corresponding vacuum line 204.Vacuum line 204 is in fluid connection with known pump devices. Pumps(not shown) are used to evacuate the air (or other gas) from theevacuation space 210 in vacuum box 202.

The evacuation space 210 is defined by the components of the upperplaten assembly 200 such that evacuation space 210 may be sealed andisolated from the ambient atmosphere. FIGS. 11, 13, and 14 show thatthis may be accomplished by placing shell mold 206 in sealed contactwith vacuum box 202. Vacuum box 202 has a gasketed seal with the outsidesurface 207 of the shell mold 206. Upper platen assembly 200 and vacuumbox 202 are adapted to function with an assortment of differing shellmolds 206. In the embodiment depicted in FIGS. 11-15, shell mold 206 isa concave or "female" mold for shaping a luggage shell. The final shapeand surface finish (smooth, faux grain leather, stippled, etc.) of ashell to be molded is determined by the mold surface 208 of the shellmold 206. Within the concavity of shell mold 206, and partially definedthereby, is form space 212.

Reference is made to FIGS. 13 and 14. Shell mold 206 is completelyperforated by a plurality of vacuum apertures (not shown) more or lessuniformly distributed over shell mold 206 generally in accordance withknown art. The apertures permit passage of air from within form space212 into evacuation space 210. In the course of the molding process, aheated sheet 216 of shell material is forced against the mold surface208 by a pressure differential induced across the shell mold 206. Thepressure differential usually is attributable to an elevated gaspressure within form space 212 and a reduced gas pressure withinevacuation space 210. Alternatively, the form space 212 may bepressurized without a concurrent depressurization of the evacuationspace 210 or, a more common alternative may be to evacuate theevacuation space 210 without affirmatively pressurizing the form space212.

In the preferred embodiment, sheet 216 is composed of ABS plastic.Alternative embodiments may use sheets of polypropylene. Otherthermoplastics may be utilized, with variable levels of success. Thepreferred pressure differential is between approximately 35 p.s.i andapproximately 40 p.s.i., with an upper limit of approximately 125 psi.Differential pressures below 35 p.s.i. must be accompanied by the use ofplastics with extremely low melt flow indexes; however, low melt flowindexes adversely affect other key material properties such as impactstrength and flexural modulus.

Lower platen assembly 240 includes support box 242, which supports theseal plate 244, and at least one pinch off plate 246 located upon sealplate 244. An optional seal key 245 may protrude from seal plate 244throughout the periphery of the seal plate 244. Seal key 245 correspondsto a seal shoulder 217 in each of side draw forms 230,232. Key 245 maycontact the undersides of side draw forms 230,232 and engage shoulder217 when upper platen assembly 200 and lower platen assembly 240 aredrawn into mutual contact, as depicted in FIG. 14. With seal key 245substantially against shoulder 217, form space 212 is sealably andsubstantially completely enclosed by shell mold 206, side draw forms230,232, and seal plate 244.

At least one gas pressure line 248 supplies gas (e.g. air) to form space212. A pump (not shown) pumps air or other suitable gas through gaspressure line 248 to elevate the fluid pressure in form space 212. Gaspressure line 248 may pass through the support box 242 and seal plate244 en route to the injection aperture 249 at the form space 212.Depending upon the particular configuration of the pinch off plate 246,pressure line 248 may pass through it as well.

Above the pinch off plate 246 are chilled corner plugs250,250',250",250'", which project from the seal plate 244 and occupylocations within the form space 212 when the two platen assemblies200,240 are brought together. For operational convenience, corner plugs250,250',250",250'" may be controllably movable up and down with respectto seal plate 244, such that they may be alternatively retracted intoand extended out of the support box 242 (by passing through sealedapertures in seal plate 244 and pinch off plate 246). Chilled cornerplugs 250,250',250",250'" serve to cool and shape preselected localizedsections of the heated sheet 216 prior to differential pressure forming.In the embodiment illustrated, corner plugs 250,250',250",250'" areshaped to provide convex or "male" forms to preliminarily shape thecorners of the shell before the final molding is accomplished by thedifferential pressure forming process. Chilled corner plugs250,250',250",250'" are in fluid communication with a source of cooledfluid (not shown), which is recirculated to and through the plugs viacoolant lines 252.

In the preferred embodiment, pinch off plate 246 is disposed upon andparallel to seal plate 244. The outer edge 247 of pinch off plate 246 isbevelled at an obtuse angle, such that the edge 247 of the pinch offplate 246 slopes outward away from the center of the plate 246throughout its periphery. When, prior to the creation of a pressuredifferential to accomplish vacuum and/or pressure forming, the side drawforms 230,232 are moved to their maximum inward position, the obliqueface of beveled edge 247 comes in close proximity to the lower edge ofthe inside faces 236,237 of side draw forms 230, 232. During pressureand/or vacuum forming of a luggage shell, the sheet 216 of shellmaterial is placed between the side draw forms 230,232 and the pinch offplate 246.

In the preferred embodiment, pinch off plate 246 is movable away fromseal plate 244. Known hydraulic or other systems control movement ofpinch off plate 246. As best indicated in FIGS. 14A and 14B, pinch offplate 246 may be moved up and down a relatively short distance, suchthat it may be in contact with seal plate 244 or spaced parallel awayand above seal plate 244. Moving the pinch off plate 246 upward tocontact the side draw forms 230, 232 severs or "pinches off" the selvageportion 222 of the sheet of thermoplastic 216, to leave a clean,uniform, trimmed edge along the formed shell.

Disposed below shell mold 206 and above seal plate 244 are at least one,but preferably two or four side draw forms 230,232. The practice of theinvention involves the movement of the side draw forms 230,232. Sidedraw forms 230,232 are movable separately from either of the platenassemblies 200,240. As best illustrated in FIGS. 12 and 15, side drawforms 230,232 are laterally movable molding elements, used to shape thefinal product. Side draw forms 230,232 are movable, as with hydraulic,pneumatic, or mechanical jacking systems or the like, radially inwardand outward from the center of the pinch off plate 246 as indicated bythe directional arrows in FIG. 12. FIG. 12 shows the side draw forms230,232 in a retracted position, withdrawn outward from the pinch offplate 246.

Controlled hydraulics are used to translate simultaneously the side drawforms 230,232 inwardly toward, or outwardly away from, pinch off plate246, as indicated by the directional arrows and phantom lines in FIGS.11 and 12. FIG. 15 shows the side draw forms 230,232 moved into aposition much closer to pinch off plates 246. As indicated from FIGS.13, 14, 14A and 14B, when, in the preferred embodiment, the side drawforms 230,232 are extended to the closed position, their inside faces236,237 protrude past the inside mold surface 208 of the shell mold 206and inwardly into the form space 212. As suggested by FIG. 11, the sidedraw forms may be retracted to a fully open position, and the insidefaces 236,237 are pulled outwardly and past the inside mold surface 208.In their fully extended, or "closed" position, the ends of the side drawforms 230,232 actually contact one another, so that the forms 230,232define an annulus surrounding the pinch off plate 246 and substantiallycircumscribing and defining the periphery of the product being molded.

The figures show an embodiment of the invention utilizing two side drawforms 230,232, each having two perpendicular legs. The motion of eachside draw form 230,232 is substantially linear along a diagonal axis, assuggested in FIG. 12. The diagonal axis of translational movement foreach form may generally be described as a line running through thecentroid of the pinch off plate 246 and through the corner of the plateproximate to the respective form 230 or 232. As each plate 230,232 movesinward, its perpendicular legs move and mold two adjacent sides of theproduct being molded.

It will be apparent to a person of ordinary skill in the art that thenumber of side draw forms utilized in the invention is variable, and maybe adapted to customize the apparatus to particular molding projects.For example, if it is desired to utilize the side draw forms to createsteep-sided depressions or deep pockets (e.g. wheel wells) in the sidesof a molded shell, it may be preferable to employ four independentlymovable side draw forms, one form for each side portion of the shell.The use of four side draw forms, while more complicated and expensive,permits each form to perpendicularly address a single respective side ofthe luggage, to form perpendicular depressions into the side of theshell. (In versions of the invention utilizing two side draw forms, eachform obliquely addresses two sides of the shell simultaneously, limitingits ability to create features perpendicularly inward into any givenside.) Still other embodiments of the invention, however, may use asingle side draw form in those instances when it is not necessary toform the entire periphery of the final product, but only one or twosides.

Side draw forms 230,232 may also be independently movable up and downbetween the two platen assemblies 200,240. For ease of illustration,FIG. 11, for example, shows side draw forms 230,232 in a loweredposition, nearly in contact with seal plate 244. FIG. 13 shows the sidedraw forms 230,232 raised up to make a sealed contact with the outerperiphery of the shell mold 206.

The manufacturing apparatus of the invention is depicted in the drawingsas having a female shell mold 206 mounted within the upper platenassembly 200, and pinch off plate 246 and seal plate 244 disposed withinthe lower platen assembly 240. It should be readily understood, however,that the entire apparatus may be inverted as to function or positionwithout arresting its function or exceeding the scope of the invention.The lower platen assembly 240, for example, alternatively may includethe shell mold and vacuum box defining an evacuation space, while theupper platen assembly 200 may be constituted from a seal plate disposedbelow a support box, with a pinch off plate hanging from the seal plate.This "upside down" embodiment may affect use of chilled corner plugs,but otherwise will meet the objectives and supply the advantages of theinvention. Similarly, acceptable alternative embodiments of theinvention may include the use of "male" shell molds, whereby the sheetof thermoplastic is forced against a convex mold.

The practice of the process of the invention, and some of itsadvantages, may now be described. Reference is made to FIGS. 11 and 12,which depict the apparatus of the invention at the very beginning of amanufacturing cycle. In FIGS. 11 and 1 2, upper platen assembly 200 isin a raised position to provide working room between it and lower platenassembly 240. For clarity of illustration, FIG. 11 shows a substantialseparation distance between the upper platen assembly 200 and lowerplaten assembly 240. In practice, the platen assemblies 200,240 mayactually be separated by a relatively small distance, sufficientseparation merely to allow the insertion of a sheet of thermoplasticmaterial (FIG. 13) therebetween.

Contact between vacuum box 202 and the outer surface 207 of shell mold206 is sealed against air leaks. The contact between seal plate 244 andsupport box 242 is likewise sealed. The selected side draw forms 230,232are installed in the retracted position (FIGS. 11, 12 and phantom linesin FIG. 13), but are then moved into the extended position (FIG. 14 andphantom lines in FIG. 11). FIG. 15 shows forms 230,232 in a positionjust short of full inward extension; at complete inward extension, thecorresponding distal ends of the legs of the forms 230,232 actually comein contact to complete a ring around the formed sheet 216. Cooled wateror other fluid is pumped through the coolant lines 252 to the cornerplugs 250,250',250",250'", and constantly recirculated, to aid inwithdrawing heat from the heated and flaccid thermoplastic sheet 216where the plugs contact the sheet. Chilled corner plugs250,250',250",250'" are in position above the pinch off plate 246 asshown in FIG. 11 or, alternatively, may be posed below the pinch offplate 246 but ready to be moved upward into the position shown in FIG.11.

A sheet 216 of thermoplastic material is heated to render it plastic andmalleable. The sheet 216 is gripped around its edges and maneuvered (upand down and to and fro) with control clamps 213,213', as depicted inFIG. 13. Control clamps 213 serve to fix and maintain the length of theoutside edge of the sheet 216. Also as depicted in FIG. 13, the twoplaten assemblies 200,240 are separated and the side draw forms 230,232positioned to allow the hot, pliable, sheet 216 of thermoplasticmaterial to be moved into a position between platen assemblies 200,240.The sheet 216 is placed centrally above the pinch off plate 246, abovethe chilled corner plugs 250,250',250",250'", and below the shell mold206 and the side draw forms 230,232.

After the heated sheet 216 is moved into position, it is brought intocontact with the surfaces of the chilled corner plugs250,250',250",250'", by lowering the sheet 216, by raising the plugs, orby raising the entire lower platen assembly 240. At this point, theplugs 250,250',250",250'", function to partially support the sheet 216.As seen in FIG. 13, the sheet 216, flaccid at elevated temperature, issupported where it contacts the chilled corner plugs 250,250',250",250'"and is unsupported elsewhere. The sheet 216 may be essentially planarwhen first placed between the platens 200,240, but its elevatedtemperature renders it moldable. Due to the effect of gravity, thecentral portion 219 of the sheet, unsupported between the plugs250,250',250",250'" may droop or sag downward, tending to assume, incross sections taken between plugs, the shape of a hanging catenary.Importantly, as the central portion 219 of the sheet 216 droopsdownward, it also tends to pull upon the selvage portion 222 of thesheet on the outside of the plugs 250,250',250",250'", thus stretchingthe sheet up and over the plugs toward the center of the pinch off plate246, as indicated by the directional arrows in FIG. 13. In this manner,thermoplastic material is moved from portions of the sheet 216 thatwould otherwise become offal to the portions of the sheet to be formedinto the final product.

A drawback of many typical vacuum or pressure formed items is weaknessin outside corners; luggage shell corners common to the current artoften crush or collapse under impact loading. This weakness is due atleast in part to the fact that conventional vacuum or pressure formingprocesses reduce the amount of shell material in the corner portions ofthe shell. Forcing the flaccid sheet of thermoplastic completely intothe extreme corners of the shell mold tends to stretch the sheet in thevicinity of corners, with the result that the sheet is there thinner andthus weaker. Less stretching of the sheet is required to push the mainportion of the sheet against the generally planar portion of the mold toform the panel portion of the shell. As a result, conventionaldifferential pressure formed luggage shells frequently are thinnest atthe corners and thickest in the main panel.

This is opposite of the optimum condition, since the corners of theshell are subject to the highest stresses and thus ideally should be thethickest and strongest part of the shell.

Another disadvantage inherent with existing pressure differentialmolding methods is that all portions of the sheet of material must bestretched, to greater or lesser degrees, to force the sheet into theshell. Because the formed shell in three dimensions has a greater totalsurface area than the original surface area of the planar piece of sheetused to form the shell, and because a fixed volume of thermoplasticmaterial is available to be forced into the mold during a givenmanufacturing cycle, a net reduction in the average thickness of thesheet must accompany the forcing of the sheet against the mold.

Advantages of the invention are thus here manifest. It is known in theart of differential pressure forming to provide plug assists to helpshape a flaccid sheet of thermoplastic immediately prior to applying thepressure differential to mold the product. In the present invention, thecorner plugs 250,250',250",250'" are shaped and selectively located tohelp pre-form only the portions of the sheet 216 that will form thecorners of the shell, and are actively cooled. The chilled corner plugs250,250',250",250'" not only help shape the sheet 216, but also reducestretching of the parts of the sheet 216 corresponding to the shellcorners. As the hot, flaccid, sheet 216 is moved to the chilled cornerplugs 250,250',250",250'", the portions of the sheet 216 actuallycontacting the plugs are cooled substantially, reducing theirplasticity. The reduced plasticity inhibits undesirable stretching inthose specific parts of the sheet 216. When the sheet 216 is formed intoa shell, the cooled portions undergo less stretching than in the priorart, and thus retain substantial thickness compared to the rest of theshell. In the present invention, the portions of the sheet 216 formingthe corners of the luggage shell are cooled by the plugs to providethicker, stronger shell corners.

FIG. 13 also shows that in the present invention much of the plasticsheet 216, specifically those portions between the chilled corner plugs250,250',250",250'", may briefly be allowed to droop immediately priorto the imposition of the pressure differential used to form a shell.This drooping in the sheet 216 mildly pre-stretches all the sections ofthe sheet 216 except the corner portions. Thus, the inventioneffectively pre-stretches the central section 219 of the sheet 216 thatwill be formed into the bottom 81 or panel portion of the shell, wherethe finished shell may acceptably be thinner. One advantage of theinvention is, therefore, that the hot flaccid sheet 216 prior to actualvacuum or pressure forming is cooled in those portions that form theshell corners, and is pre-stretched in those sections that form theshell panel, resulting in a vacuum-formed shell with stronger corners,but a slightly thinner panel.

Another advantage of the invention is that it increases the net volumeof thermoplastic material available for molding into the final product.This increase is due to enhanced efficiency of materials use, without anet increase in actual materials requirements.

Some shell material droops downward and outward from the corner plugs250,250',250",250'", and eventually is sandwiched between the shell mold206 and the seal plate 244. Before the shell material is clamped betweenthe undersides of the shell molds 230,232 and the seal plate 244,however, the sheet 216 is allowed to sag between the corner plugs250,250',250",250'", as previously described. As a result of thissagging, the selvage portion 222 of the sheet is stretched, since theedges of the sheet 216 are fixedly held by control clamps 213,213. Thisstretching is manifested by some sliding of the sheet 216 inwardly overthe tops of the plugs 250,250',250",250'", as shown by the directionalarrows of FIG. 13. This sliding and stretching results in a movement ofa net volume of thermoplastic material radially inwardly into themarginal portion from the selvage portion 222 of the sheet 216. Materialalso moves up and over the corner plugs 250,250',250",250'", slidingpast them into and toward the central portion 219. A net increase isrealized in the volume of thermoplastic material in the portion of thesheet 216 in a confronting relation with the mold 206; the beneficialconsequence of this movement of thermoplastic material is that morematerial is available, from a given sheet 216, to be forced against themold 206. A comparatively reduced volume of material remains in theselvage portion 222 of the sheet.

With the increase in material volume available for molding against themold 206, the undesirable stretching of the sheet 216 to fit the moldsurface 208 (especially the corners) is mitigated. More availablematerial volume results in a thicker molded shell wall, producing acomparatively stronger shell. The finished shell product accordingly hasincreased performance without an increase in materials requirements.

Reference is made to FIG. 13. Once the sheet 216 has been pre-stretchedto optimum conditions according to the foregoing disclosure, and shortlyafter the time the sheet 216 contacts the corner plugs, the seal plate244 and side draw molds 230,232 are moved together (perhaps by movingone or both platen assemblies 200,240) to clamp the offal or selvageportion 222 of the sheet 216 between the seal key 245 and the undersideof the side draw forms 230,232. The clamping together of the seal plate244 and the side draw forms 230,232 provides an annular seal around theform space 212, with the selvage 222 acting as a provisional gasket.(The side draw forms 230, 232 may be sealed to the seal plate 244 usingother methods, but the overall object is to sealably and substantiallycompletely enclose the form space 212.) In the preferred embodiment, theform space 212 at this point in the process is entirely surrounded bythe shell mold 206, the seal plate 244, and the side draw forms 230,232.The platen assemblies 200,240 may be releasably locked together toassure properly sealed enclosure of the form space 212.

Pressurization of form space 212 and evacuation of the evacuation space210 are then initiated. Air or inert gas is pumped rapidly through theair pressure line 248 and into form chamber 212, while concurrently airis pumped out of evacuation space 210 through vacuum line 204. Theresult is a sudden reduction of pressure in the evacuation chamber 210and an elevation of pressure in the form chamber 212. These pressurechanges induce a pressure differential across shell mold 206, and gas isthereby caused to flow from the form space 212 to the evacuation space210 via the vacuum apertures in the shell mold 206. Substantially inaccordance with known principles of the art, the pressure differentialacross the shell mold 206 and the forced passage of air through theholes penetrating the shell mold 206 give rise to a corresponding fluidpressure differential across the sheet 216 itself. The pressuredifferential is due to a lower pressure between the sheet 216 and theshell mold 206 than the pressure between the sheet 216 and the sealplate 244. The pressure differential rapidly forces the flaccid sheet216 firmly against the inside surface 208 of the shell mold 206, asdepicted in FIG. 14. The use of the pressure differential to press thesheet 216 against the shell mold 206 is the "differential pressureforming" step of the process. The pressure differential is maintainedfor a period of time to insure that the sheet 216 is thoroughlyimpressed with every feature of the inside mold surface 208.

The imposition of the pressure differential and the pressing of thesheet 216 against the shell mold 206 is initiated while the side drawforms 230,232 are in an extended position, closed toward the pinch plate246, and constituting a side mold completely around the periphery of theform space 212, as illustrated in FIGS. 13 and 14.

FIG. 14 shows that the elevated pressure in form space 212 forces amargin of sheet 216 against the inside faces 236,237 of the side drawforms 230,232. The inside faces 236,237 of the side draw forms 230,232may be shaped or textured so as to mold the marginal portion of sheet216 pressed against them. The inside faces 236,237 preferably areremovably attachable to the interior ends of their respective draw forms230,232, and may be plates or blocks that bolt onto or slip onto (e.g.key-and-slot interlock) the forms 230,232. Because inside faces 236,237preferably are removable, they are interchangeable independently fromthe side draw forms 230,232 and from the main shell mold 206.

The invention thus makes it possible to vary the appearance, shape, oreven the size (i.e. depth) of the molded shell without changing theentire shell mold 206. The side draw forms 230,232 also areinterchangeable with respect to the shell mold 206, but the preferredembodiment allows the user to customize or adapt his product by merelyswitching the inside faces 236,237. Particular individual inside faces230,232 may be configured to mold bumper strip channels, and/orlocational indicia for hardware attachment, and/or aesthetic lines,logos, ridges, and/or the like into the final product shell. Likewise,the inside faces 230,232 may be configured to mold into the final shella desired structural feature, for example a wheel well and/or a handlerecess.

Similarly, the assorted sets of inside faces 230, 232 useable with aparticular corresponding side draw form 230,232 and a given shell mold206 may be of differing dimensions. By interchanging a narrower (i.e.shorter) or a wider inside face component, the overall depth of themolded container or shell may be varied from cycle to cycle without theneed to exchange and replace the shell mold 206 or the side draw forms230,232. An advantage of the invention therefore is that the independentinterchangeability of the inside faces 236,237 permits many permutationsin the appearance and/or structure of the finished shell using acomparatively limited number of different shell molds 206 and side drawforms 230,232.

FIGS. 14A is an enlarged sectional view depicting in detail the moldingof the margin 220 of sheet 216 by a side draw form 232. Side draw form232 extends inward, preferably past the inside surface 208 of shell mold206 and correspondingly molds a marginal portion 220 of the sheet 216.The margin 220 may be shaped by the side draw form 232 to create a wallmember element 42 and a flange 44, as those elements are similarlydepicted (labelled 42 or 82 and 44 or 84, respectively) in FIGS. 4 and5. The main or central portion of the sheet material 216 shown in FIG.14A constitutes the bulk of the shell 40 or 80 as shown in FIGS. 4 and5. Side draw forms 230,232, therefore, mold the shell 40,80 of theluggage case of the preferred embodiment to provide the frame featuredefined by the wall members 42,82 and flanges 44,84 as described inFIGS. 1-8 and hereinabove, as well as other shell features, such asbumper strip channels and the like.

Thus, side draw forms 230, 232 mold the margins of the sheet 216 whicheventually comprise the peripheral frame portion of the finished shell(and may be configured to shape the side or other portions of the shellas well). When the hot sheet 216 is pressed against the inside of theshell mold 206, it simultaneously is forced against the side draw forms230,232 which project inward into the form space 212. The portion of thesheet 216 disposed between the forms 230,232 and the pinch off plate 246is transformed from a planar sheet to a shape having the cross sectionshown in FIGS. 14 and 14A. FIGS. 4 and 8 considered together with FIG.14 illustrate how the use of the side draw forms 230,232 molds themargins of the sheet 216 to form the flanges 44,84 and wall members42,82 of the finished shell 40, 80. FIG. 14A also provides detail ofseal key 217 crimping the offal or selvage portion 222 of the sheet 216against shoulder 217 in draw form 232.

After the side draw plates 230,232 have been moved into the extendedposition shown in FIGS. 14 and 14A to form the margin 220 of the sheet216, the sheet 216 is maintained in the configuration of FIG. 14 for abrief period longer. An optional feature of the invention may then beengaged to trim the selvage 222 from the margin 220 of the sheet 216.Presently in the art, excess shell material is cut off from the moldedshell using a bandsaw or the like in a separate process step after thecompletion of differential pressure forming. FIGS. 14, 14A, and 14B incombination illustrate how pinch off plate 246 may be used to sever thesheet 216. FIGS. 14A and 14B are enlarged sectional views of that partof FIG. 14 showing that side draw form 232 forms margin 220 of sheet 216inwardly past shell form 206 to close proximity to, or even mild contactwith, the pinch off plate 246. Pinch off plate 246 is movable, e.g.hydraulically, in a direction perpendicular to the seal plate 244, asindicated by the directional arrow in FIG. 14A. Pinch off plate 246normally is in parallel position and contact with the underlying sealplate 244, upon which pinch off plate 246 rests. A powered mechanism(not shown), perhaps disposed below the seal plate 244 and within thesupport box 242, extends through the seal plate 244 to the pinch offplate 246.

After the differential pressure forming of the sheet 216 against theshell mold 206 and the side draw forms 230, 232 has been completed (FIG.14A), the pinch off plate 246 is moved a small distance upward and awayfrom the seal plate 244 to the position illustrated in FIG. 14B.Movement of the pinch off plate 266 preferably occurs immediately priorto the vented release of pressure from within the form space 212 and thetermination of the pressure differential across the shell mold 206. Inthis manner, the pressure differential holds the sheet 216 in placeduring the pinching-off process. FIG. 14B shows that the movement of thepinch off plate 246 pinches the sheet 216 between the oblique face 247of the plate 246 and a lower edge of draw form 232. Pinch off plate 246may be brought into contact with form 232, in which instance sheet 216may be completely cut between the two contacting components 232,246. Theside draw form 232 thus serves as a type of immobile cutting blockagainst which the pinch off plate 246 may act. Pinch off plate 246 thussevers the selvage 222 (i.e. the part of the sheet 216 below the drawform 232) from the margin of the sheet 216 (the portion of the sheet 216above the oblique face 247 of the pinch off plate 246 and interior tothe shell mold 206). Alternatively, the face 247 of the plate 246 may bemoved proximate to the edge of the form 232, but not in contacttherewith, as shown in FIG. 14B, to constrict the sheet 216 withouttotally severing it. In this manner, the sheet 216 is permanentlycreased to facilitate later separation of the offal from the shell. Thepinching of the sheet 216, either to completely sever or to crease it,provides for a clean, uniform cut of the sheet 216 between margin 220and selvage 222. Such a cut should be uniform, since it occurs alongwhat eventually constitutes the peripheral edge 48 or 88 of the shell 40or 80 as shown in FIGS. 1, 2 and 4.

An advantage of the invention is that the peripheral edges 48,88 areexposed, not covered by an expensive, cumbersome metal frame, but ratherare exposed, providing economy, aesthetics and easy case closure. Theperipheral edges 48,88 preferably are milled or machined to a pleasantsmoothness, perhaps using a computer-guided edging tool.

After the pinch off plate 246 has been moved, if desired, to pinch thesheet 216 (FIG. 14B), the sheet 216 is held against the shell mold 206just long enough to allow it to cool and harden. Once shell sheet 216has cooled, it loses its plasticity and becomes rigid in the generalshape and form of the final product.

As mentioned, the side draw pulls 230,232 are movable radially outwardfrom the extended positions shown in FIGS. 13, 15, and 14 and in phantomlines in FIG. 11 to the retracted position shown in FIGS. 11 and 12 andin phantom lines in FIG. 13. While the imposed pressure differentialholds sheet 216 firmly against shell mold 206 and the inside faces 236,237 as shown in FIG. 14, the side draw pulls 230,232 are actuated andcontrollably moved, substantially parallel to and between the platenassemblies 200,240, outward from the position depicted in FIGS. 13 and14. The side draw forms 230,232 are pulled away from the cooled sheet216 and retracted outward to the position shown in phantom lines in FIG.13, and in FIGS. 11 and 12. The platen assemblies 200,240 are then movedapart to permit sheet 216, now a molded shell, to be removed from themolding apparatus for further finishing as needed, attachment ofhardware and linings, and the like.

It is observed that the movable side draw forms 230,232 permit theformation into the shell of substantial shell wall members 42,82, whichdepend inwardly from the shell itself at angles of about ninety degrees,and yet also permit the molded shell easily to be removed from the shellmold 206. The movable character of the side draw forms 230,232 overcomesthe disadvantage of the known art, in which the pressure differentialforming of such substantial projections would effectively prevent themolded shell from being removed from the shell mold 206. Were the sidedraw forms 230,232 not radially outwardly movable, the annular wallmember 82 of a formed shell 80 would be locked against the top of theimmobile side draw form against which the wall member 82 was pressed,and the entire shell would effectively be permanently molded within itsown mold. Conversely, without the ability to mold a significant,substantially perpendicularly projecting wall member 82, dependingeither inwardly or outwardly from the main or central portion of theshell, an effective increase in the moment of inertia of the shell, andthus the molding of an integrally formed frame element, wouldeffectively be precluded using differential pressure molding. Thepresent invention overcomes the shortcomings of known systems bypermitting the molding of integrally formed container frames consistingof substantial projecting wall 82 and flange 84 elements, while alsopermitting the retraction of the mold components 230,232 used to shapethe integral frame to allow the separation of the molded container fromthe mold 206.

Although the invention has been described in detail with particularreference to these preferred embodiments, other embodiments can achievethe same results. Variations and modifications of the present inventionwill be obvious to those skilled in the art and it is intended to coverin the appended claims all such modifications and equivalents. Theentire disclosures of the patents cited hereinabove are herebyincorporated by reference.

We claim:
 1. A process for molding a shell from a sheet of plasticmaterial, the shell having a bottom and side portions extending from thebottom to a peripheral edge, the intersection of two side portions andthe bottom generally defining a shell corner, the process comprising thesteps of:(a) heating the sheet of plastic material, the sheet having acentral portion, a marginal portion, and a selvage portion; (b)providing a mold means having a mold surface of a shape corresponding tothe shell; (c) providing a form space defined in part by the moldsurface; (d) providing at least one movable side draw form extendinginto the form space; (e) positioning the central portion of the sheet inthe mold means opposite the mold surface; (f) providing a clamp remotefrom the mold surface; (g) clamping the selvage portion of the sheet;(h) disposing four rigid, upwardly extending, corner plugs within theform space; (i) contacting the sheet with the four corner plugs anddeliberately allowing the sheet to droop and sag by gravity between allfour plugs to pre-stretch the central portion of the sheet; (j) allowingthe heated sheet to slide inwardly over the four corner plugs and intothe form space prior to forcing the central portion against the moldsurface; (k) conforming the central portion of the sheet to the moldsurface to form the bottom and the side portions of the shell; (l)forcing the marginal portion of the sheet against the side draw form,thereby shaping the marginal portion to fashion a frame integrallyformed with the central portion, said frame extending substantiallycontinuously along at least one of the side portions of the shell, andsaid frame comprising a wall member and a flange, said forcing stepcomprising:bending the marginal portion to form the wall memberextending into the form space from the side portion of the shell; andfashioning the flange so that said flange extends from the wall memberto the selvage portion and is disposed at an angle with respect to thewall member and to the selvage portion; (m) laterally retracting theside draw form to a retracted position substantially outside the formspace; (n) only after laterally retracting the side draw form, removingthe shell from the mold surface; and (o) severing the selvage portion ofthe sheet from the flange to free an edge of the flange whereby, afterthe step of severing, the peripheral edge is defined by the free edge ofthe flange.
 2. The process of claim 1 wherein the step of heating thesheet of plastic material comprises heating a sheet ofacrylonitrile-butadiene-styrene.
 3. The process of claim 1 wherein thestep of heating the sheet of plastic material comprises heating a sheetof polypropylene resin.
 4. The process of claim 1 wherein the step ofproviding a mold means comprises providing a means for vacuum formingthe sheet of plastic material against the mold surface.
 5. The processof claim 1 wherein the step of conforming the the central portion of thesheet to the mold surface comprises supplying a pressure differentialacross the sheet to force the sheet against the mold surface.
 6. Theprocess of claim 5 wherein the step of supplying the pressuredifferential comprises:(a) inducing a vacuum on one side of the sheet;and (b) applying air pressure to the other side of the sheet.
 7. Theprocess of claim 5 wherein the step of supplying a pressure differentialcomprises providing a upper platen assembly movably disposed paralleland next to a lower platen assembly.
 8. The process of claim 7 furthercomprising:(a) stretching parts of the sheet prior to supplying thepressure differential; and (b) retarding stretching of selected sectionsof the sheet which form the shell corners.
 9. The process of claim 8wherein the step of retarding stretching of sections of the sheetfurther comprises:(a) disposing at least one corner plug between theupper platen assembly and the lower platen assembly plug to help shapeat least one shell corner; (b) cooling the corner plug; and (c) placingthe heated sheet in contact with the corner plug.
 10. The process ofclaim 1 wherein the shell is a shell of a luggage case, and wherein theframe defines a hinged opening of the luggage case.
 11. The process ofclaim 1 wherein the shell is a shell of a luggage case, and wherein theframe defines a hinged opening of the luggage case.
 12. The process ofclaim 1 wherein the step of severing the selvage portion of the sheet isperformed while the central portion of the sheet is conformed to themold surface.
 13. The process of claim 12 wherein the step of severing aselvage portion comprises:(a) providing a movable plate proximate to thesheet; (b) moving the plate toward a fixed block; (c) pinching the sheetbetween the block and the movable plate; and (d) separating the sheetfrom the mold surface after the sheet has been pinched.
 14. A processfor molding a luggage shell from a sheet of thermoplastic material, theluggage shell having a bottom, corner portions, and side portionsextending from the bottom to a peripheral edge, comprising the stepsof:(a) heating a sheet of thermoplastic material, the sheet having amarginal portion at least partially surrounding a central portion and aselvage portion at least partially surrounding the marginal portion; (b)partially surrounding a form space with a mold surface; (c) placing atleast one movable side draw form in an extended position protruding atleast partially into the form space; (d) providing a clamp remote fromthe mold surface; (e) clamping the selvage portion of the sheet; (f)disposing four rigid upwardly extending corner plugs in the form space;(g) contacting the sheet with the four corner plugs and deliberatelyallowing the sheet to droop and sag by gravity between all four plugs topre-stretch the central portion of the sheet; (h) allowing the heatedsheet to slide inwardly over the four corner plugs prior to forcing thecentral portion against the mold surface; (i) forcing the centralportion of the heated sheet against the mold surface; (j) forcing themarginal portion of the heated sheet against the side draw form, whilethe side draw form is in the extended position, thereby shaping themarginal portion to define a frame, said frame comprising a wall memberand a flange, along the peripheral edge, said step of forcingcomprising:bending the marginal portion to form the wall memberextending at an angle from the side portions into the form space; andfashioning said flange extending from the wall members and disposed atan angle with respect to the bottom; and (k) translating parallel to thewall member the side draw form to a retracted position substantiallyoutside the form space while the central portion is against the moldsurface.
 15. The process of claim 14 further comprising the steps of:(a)severing the selvage portion of the sheet from the marginal portion; and(b) separating the central portion of the sheet from the shell moldafter severing the selvage portion.
 16. The process of claim 15 whereinthe step of severing the selvage portion further comprises:(a) disposinga block means on one side of the sheet; (b) providing a movable platemeans on the other side of the sheet; (c) moving the plate means towardthe block means; and (d) pinching the sheet between the plate means andthe block means.
 17. The process of claim 14 further comprising the stepof substantially impeding the thinning of selected sections of the sheetcorresponding to the corner portions of the shell.
 18. The process ofclaim 17 wherein the step of substantially impeding the thinning ofselected sections of the sheet comprises cooling the sections of thesheet prior to forcing the central portion of the heated sheet againstthe mold surface.
 19. The process of claim 18 wherein the step ofcooling the sections of the sheet comprises chilling said corner plugs.